Nongaseous pyrotechnic delay mixture



June 27, 1961 I R. H. cOMYN v 2,990,264

NONGASEOUS PYROTECHNIC DELAY MIXTURE Filed Aug. 3, 1950 INVENTOR. RAYMOND H. COMYN BY RM T F-Q r K Uflfiw ATTYS able gas evolution therefrom.

United Statesv Patent (3 2,990,264 NONGASEOUS PYROTECHNIC DELAY MIXTURE Raymond This invention relates to a nongaseous pyrotechnic delay mixture for use in a projectile, rocket, flare, smoke float, or any other ordnance missile or device and is particularly adapted to cause initiation of the explosive or propellent charge, light or smoke emitting pyrotechnic mixture, as the case may be, in time delayed relation with respect to the initial ignition thereof by the usual igniter associated therewith. Heretofore, gasless delay compositions used in ordnance missiles and devices by the armed forces for delaying the ignition of the pyrotechnic mixtures or explosives therein such, for example, as a bursting charge, propellent charge, light or smoke emitting composition as the case 'may be, have not been altogether satisfactory for the reasons that such compositions were'susceptible to changes in gas pressure and thus the burning range thereof was affected by the gas pressure produced therefrom during ignition and burning of 'such compositions thereby causing erratic burning rate thereof. Furthermore, such compositions lack stability, in that they would absorb sufficient moisture to reduce the efliciency and effect the burning rate thereof and upon numerous occasions fail to function altogether at low temperature particularly after being stored over a long period of time. Such compositions also proved not altogether satisfactory for the purpose intended inasmuch as the burning rate was erratic and unpredictable and the ignition sensitivity character- -istic thereof was nonuniform.

' The present invention is especially compounded to overa come the aforesaid objections found in prior art compositions and to provide a new and improved nongaseous 1delay mixture having the admirable characteristic of stability, sensitivity and uniform burning rate without notice- An object of this invention is to provide a new and improved nongaseous delay mixture for use in an ordnance missile or device which forms solid combustion products,

and does not evolve an appreciable amount of gas during burning thereof.

Another object of the invention is to .provide a stable nongaseous delay mixture having an ignition temperature lower than the burning temperature of the igniter associated therewith and which is ignited bythe igniter whereupon the burning range of the mixture is unaffected by the gas pressure produced during the burning thereof.

Another object of the invention is to provide a sensitive nongaseous delay mixture whose burning rate is predict- "able, and which produces suflicient heat at a high'temperature to ignite either a detonator or a relay igniter,

as the case may be.

An additional object is to provide a method of producinga nongaseous pyrotechnic delay mixture.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following deice tailed description when considered in connection with the accompanying drawing wherein:

One adaptation of the invention is illustrated in the accompanying drawing which is a fragmentary longitudinal sectional view of an ordnance device.

The missile comprises the usual shell or casing 10 having a normally locked firing pin 11 adapted to be moved to a firing position in engagement with the primer 12 upon impact of the missile with a target, it being understood, however, that the firing pin is released for movement to the firing position when the detents 13 are moved out of engagement therewith by centrifugal force as the missile travels along a trajectory. Arranged within the cavity 14 formed in the shell 10 and having an igniter 15 on one end, and an igniter 16 on the other end thereof is the nongaseous delay mixture 17 of the present invention, the igniter 15 being adapted to be ignited by the primer 12 when the firing pin is moved to the firing position, whereupon the delay mixture is ignited by the igniter 15 and will burn at a predetermined rate, without noticeable gas evolution therefrom for a predetermined period of time such, for example, as from 3.83 to 4.05 seconds whereupon the igniter 16 is ignited by the delay mixture and thus the booster charge 18 is fired in time delayed relation with respect to impact of the missile with the .ing of the manganese with the lead chromate and barium .chromate. This is done to protect the manganese from deterioration.

The treatment with potassium dichromate serves to modify the surface of the manganese particles for the sub sequent stearic acid treatment. Although it is not known exactly what occurs during treating of the manganese with potassium dichromate it is thought that an oxide coatingforms on the manganese particles to provide 'a bond for the stearic acid. The carbon tetrachloride acts as a solvent for the stearic acid and as a lubricant during the mixing process. The stearic acid is chemisorbed on the manganese surface and acts as a moisture absorption inhibiter to prevent deterioration during storage due to moisture. As is obvious to those skilled in the art, the aqueous residue of the finished product is removed therefrom in any suitable manner, such, for example, as drying in order to obtain a dry powdered mix. The concentration of the potassium dichromate solution and the carbon tetrachloride-stearic acid solution is not critical, and any concentration thereof serving the purpose is suitable.

A typical mixture producing satisfactory stability, sensitivity, burning rate and showing no appreciable gas evolution while burning is as follows:

Percent Manganese 35 It will be understood, however, that the proportions of these ingredients may be varied, if desired, to meet the requirements of various uses of the mixture. For example, when a faster burning rate is required a satisfactory composition may be obtained by reducing the proportions of or completely eliminating the barium chromate, and when a slower burning rate is desired the proportion of the lead chromate in the composition is reduced.

The mixing of the ingredients may be accomplished in any suitable manner and during such mixing operation carbon tetrachloride may be added to reduce particle friction of the ingredients to a sufiiciently low value to facilitate mixing.

Both wet and dry methods of mixing the ingredients have been tested and from such tests it has been found that while both methods are satisfactory the dry method of mixing in certain cases is most successful and has produced the best results. Furthermore, when the dry method is employed it does not require drying and regrinding after mixing as is the case when employing the aforesaid wet method. In preparing the ingredients com prising the nongaseous delay mixture of the instant invention it has been found that most satisfactory results are obtained when the manganese is of a particle size such, for example, as 100% less than the U.S. standard sieve, mesh size 325/000, the lead chromate is of such a particle size as to readily pass through a U.S. standard sieve, mesh size 200/000, and the barium chromate of such a particle size as to pass through a U.S. standard sieve, mesh size 325/000. When the aforesaid preparation has been completed the ingredients are then thoroughly mixed in any suitable manner but preferably by placing them in a mixing device, the device being of any type suitable for the purpose such, for example, as the type known in the trade as the Simpson mixer. During the mixing operation a quantity of carbon tetrachloride may be added to the ingredients, if desired, thereby reducing the friction between the particles thereof and also insure thorough mixing of the ingredients. The time period required to mix the aforesaid ingredients thoroughly when the mixer is set in operation is approximately 30 minutes, the ingredients being subjected to a mulling action as the mixer operates.

It has been found that ingredients comprising mixtures of this type may segregate during wet mixing with the light materials coming to the top, and it is probable that this condition may also occur during dry mixing of the ingredients and thus this effect can be minimized by employing chemicals as heretofore described, with densities and particle sizes which are approximately in the same range. improved by employing a few chemicals as possible, such, for example, as disclosed in the instant invention, rather than four or five chemicals, as heretofore used in prior art devices.

It will be understood, however, that as either the metallic fuel or the oxidant in a mixture is increased over the amount necessary for maximum heat, the reaction heat measured in calories per gram, will decrease. An excess of metallic fuel is undesirable; while an excess of oxidant will tend to decreaes the burning rate of the mixture. However, a large excess of an oxidant may be undesirable if the oxidant releases its oxidizing element very easily.

The use of an inert diluent provides another method of reducing the reaction heat and the burning rate of the mixture. However, there is the possibility of actually stopping the whole reaction if the mixture is uneven. By the addition of a second oxidant, as heretofore described, which reacts with the fuel at a slower rate than the first oxidant thereby providing an effective method of slowing the burning rate of the mixture, and thus as long as the fuel and both of the oxidants are present in stoichiometric proportions, the danger of bubbles due to a sud- Furthermore, it has been found that mixing is 4 den excess of oxygen being released by the oxidant is decreased whereupon uniform and complete burning of the mixture is insured.

It is well known in the art of delay mixtures that moisture accelerates the deterioration of gasless delay mixtures, such conditions resulting from the reaction of the ingredients of the mixture with moisture as well as from ionic reactions which are promoted by the solvent action of the moisture. In view of these conditions existing in prior art mixtures the instant invention overcomes such conditions by providing a mixture having the desirable characteristics of low water solubility; free from hydrate formation, and not subjected to decomposition in water.

The particle size of the oxidant does not affect the properties of a gaseless delay element as much as the particle size of the fuel. As the particle size decreases and the surface thereof increases, acceleration of, the burning rate of the gaseless delay element and surveil lance deterioration thereof may be expected. However, it is desirable to use a fuel whose particle size lies in the subsieve range for the reason that they ignite more readily as the size decreases.

During tests, the gasless delay mixture and the starter and relay igniter compositions therefor were loaded in a steel test body at pressures from 10,000 to 35,000 p.s.i., the delay element being composed of three equal increments and disposed between the aforesaid igniters. The exposed top portion of the started composition was ignited by any convenient means, whereupon the delay element proved to be sufficiently sensitive to be ignited by the starter igniter, the time required for the delay element to burn to the bottom was substantially 4.05 seconds, the burning temperature thereof being sufliciently high to cause ignition of the relay igniter. Furthermore, the test proved that the gasless delay mixture burned evenly and at a relatively slow rate when ignited, without noticeable gas evolution therefrom.

In loading the gasless delay mixture into the delay cavity of an ordnance missile or device it has been found that the best results were obtained when the aforesaid increments were pressed into the cavity at a pressure of 10,000 to 35,000 p.s.i.

From the foregoing, it will be understood, that a gasless delay mixture for an ordnance missile or device has been compounded either by wet or dry mixing methods disclosed herein and having new and improved characteristics such, for example, as uniform mixing and surveillance qualities; whose burning range is unaffected by the gas pressure produced during burning thereby permitt'ing the delay mixture to burn evenly until entirely consumed; and which is sufliciently sensitive to be ignited by the starter igniter and to furnish suflicient heat at a high enough temperature to ignite either a relay igniter or a detonator, as the case may be, and which will not evolve an appreciable amount of gas during burning thereof.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. The method of producing a nongaseous pyrotechnic delay mixture which comprises the steps of first treating a quantity of powdered manganese with a hot aqueous solution of potassium dichromate and then with a carbon tet rachloride solution of stearic acid, mixing the treated manganese with quantities of lead chromate and barium chromate for about thirty minutes, adding carbon tetrachloride to the mixture during the mixing operation in a quantity sufficient to reduce the particle friction between the ingredients thereby to facilitate the mixing thereof, and drying the mixture upon completion of the mixing operation, the quantities of manganese, lead chromate and barium chromate being such that each constitutes approximately one-third of the mixture.

2. A nongaseous pyrotechnic delay composition which is composed of a deterioration inhibited mix of Which manganese constitutes the principal bulk, said mix containing manganese commingled with potassium dichromate and stearic acid; lead chromate; and barium chromate; the quantities of said mix, lead chromate and bari- 1,877,127 Hale Sept. 13, 1932 2,146,033 Seavey et a1. Feb. 7, 1939 2,450,892 Hale Oct. 12, 1948 2,457,860 Bennett et al. Ian. 4, 1949 2,478,918 Hale et a1 Aug. 16, 1949 2,696,429 Hart Dec. 7, 1954 

1. THE METHOD OF PRODUCING A NONGASEOUS PYROTECHNIC DELAY MIXTURE WHICH COMPRISES THE STEPS OF FIRST TREATING A QUANTITY OF POWDERED MANGANESE WITH A HOT AQUEOUS SOLUTION OF POTASSIUM DICHROMATE AND THEN WITH A CARBON TETRACHLORIDE SOLUTION OF STEARIC ACID, MIXING THE TREATED MANGANESE WITH QUANTITIES OF LEAD CHROMATE AND BARIUM CHROMATE FOR ABOUT THIRTY MINUTES, ADDING CARBON TETRA- 